Non-corrosive stripping and cleaning composition

ABSTRACT

A non-corrosive photoresist stripping and cleaning composition, comprising:  
     (a) about 5% to about 50% of a solvent;  
     (b) about 10% to about 90% of an alkanolamine;  
     (c) about 0.1 to 10% of a carboxylic acid; and  
     (d) about 1.0% to 40% of water.

[0001] This is a Continuation-In-Part of U.S. patent application Ser.No. 08/850,991, filed May 5, 1997.

[0002] The present invention relates to a non-corrosive photoresiststripping and cleaning composition containing a combination of certainpercentages of (1) selected solvents; (2) selected alkanolaminecompounds; (3) selected corrosion inhibitors; and (4) water.

BACKGROUND OF THE INVENTION

[0003] The photoresist stripper/plasma etch residue cleaner art isreplete with numerous references to compositions containing either apolar solvent or an alkanolamine compound, or both. The presence of analkanolamine in photoreist stripper compositions has been judged to beessential to effectively remove cross-linked resist films. However,alkanolamine-type photoresist strippers sometimes have a serious problemof corrosion, especially with aluminum substrates.

[0004] It is believed that the corrosion is caused in part by theionization of water with the alkanolamine in post-stripping water rinse,as residual stripper solution may be retained on the substrate surfaceand/or substrate carrier after the stripping step. In other words, thealkanolamine component of the stripper composition does not corrode thesubstrate by itself, but can trigger water to cause the corrosion.

[0005] To solve this problem, an intermediate rinse step with an organicsolvent (e.g., isopropyl alcohol) has been used between the strippingstep and the post-stripping rinse with water. However, such intermediaterinses are not necessarily desirable because overall stripping operationbecomes more complicated and, furthermore, an additional solvent wasteis produced. Accordingly, if alkanolamine-containing strippers are to befurther employed, there is a need to solve this corrosion problemwithout generation of intermediate organic solvent wastes.

[0006] In addition, other mechanisms of metal corrosion are known. Forexample, metal halides, such as aluminum chloride, tend to be generatedas plasma-etch by-products. Metal halides may cause corrosion ofsubstrates when contacted with water from a water rinse following thecleaning process. Another corrosion mechanism is observed especiallywith alloys such as Al—Cu—Si during cleaning or in a post-clean rinseprocess. This type of corrosion is usually observed locally and isreferred to as pitting. Pitting is thought to be caused by the galvanictype of the electrochemical reaction between two metals which havedifferent electronegativities.

[0007] The present invention provides a solution for all theabove-described types of corrosion.

[0008] Furthermore, during anisotropic plasma etching processes for viacontacts, metal patterns, and passivation openings, “sidewall residues”are frequently deposited on the resist sidewall. After the oxygen plasmaashing of photoresist films, these residues become metal oxides.Incomplete removal of these residues interfere with the patterndefinition and/or complete filling of via holes.

[0009] Several different chemistries have been identified for removingthe post-etch residues, particularly the metal oxide type. For example,alkaline aqueous developers such as those containing tetramethylammoniumhydroxide (TMAH) are known to attack aluminum. Thus, an aluminum oxideresidue can be etched away with TMAH. However, other types of thepost-etch residues associated with multi-metal systems such as Al—Si—Cucannot be so easily removed with TMAH. TMAH also is ineffective onresidues formed from polysilicon plasma etch processes.

[0010] The metal oxide type sidewall residues can also be removed with:(1) a mixture of hydrofluoric acid and ethylene glycol ether, or (2) amixture of nitric acid, acetic acid, and hydrofluoric acid. Thesesolutions require extreme process control to prevent excessive attack ofcritical metal and oxide layers. In some device structures, thesesolutions are not useful because of their nonselective attackmechanisms.

[0011] Wai M. Lee described at Interconnects, Contact Metallization andMultilevel Metallization Symposium (183rd Spring Meeting of TheElectrochemical Society) in Honolulu, Hi., May 16-21, 1993, that ahydroxylamine-containing amine/water-based stripper composition canremove some kinds of the sidewall residues. Although hydroxylamine has apotential to enhance the stripperability and/or the metal corrosioninhibition, it is not stable upon heating. Therefore, the use ofhydroxylamine is not recommended, especially when used in a highlyalkaline medium.

[0012] Accordingly, hydroxylamine is not suitable for use in strippingof photoresist films or cleaning of the post-etch residues at highertemperatures.

[0013] Illustrative of references suggesting photoresist stripping orplasma-etch residue cleaning compositions containing a polar solventand/or an alkanolamine compound are the following:

[0014] U.S. Pat. No. 4,617,251, which issued to Sizensky et al. on Oct.14, 1986, teaches a positive photoresist stripping compositioncontaining: (A) selected amine compound (e.g., 2-(2-aminoethoxy)ethanol,2- (2-aminoethylamino)ethanol, and mixtures thereof) and (B) selectedpolar solvents (e.g., N-methyl-2-pyrrolidinone, tetrahydrofurfurylalcohol, isophorone, dimethyl sulfoxide, dimethyl adipate, dimethylglutarate, sulfolane, gamma-butyrolactone, N,N-dimethylacetamide andmixtures thereof). The reference further teaches that water as well asdyes or colorants, wetting agents, surfactants and antifoamers may beadded into this composition.

[0015] U.S. Pat. No. 5,279,791, which issued to Lee on Jan. 18, 1994,teaches a stripping composition for removing resists from substratescontaining (A) hydroxylamine (e.g., NH₂OH); (B) at least onealkanolamine; and optionally (C) at least one polar solvent.

[0016] European Patent Application No. 647884 assigned to J. T. BakerInc. discloses nonaqueous photoresist stripper composition comprising(i) a stripping solvent (e.g. N-methyl-2-pyrrolidinone), (ii) anucleophilic amine (e.g., monoethanolamine), and (iii) a reducing agentsuch as salicyl aldoxime, gallic acid, and gallic acid esters.

[0017] European Patent Application No. 596515 assigned to J T Baker,Inc. discloses an alkaline photoresist stripping composition comprisinga solvent, a nucleophilic amines (e.g., 1-amino-2-propanol,2-aminoethanol), and a non-nitrogen containing weak acid

[0018] German Published Patent Application No. DE3828513, which issuedto Schulz on Mar. 1, 1990, teaches a positive and negative photoresiststripper composition containing (A) an aprotic polar solvent (e.g.,1,3-dimethyl-2-imidazolidinone or 1,3-dimethyl-tetrahydropyrimidinone);and (B) an organic base (e.g., alkanolamine).

[0019] Japanese Published Patent Application No. 1-081949, which issuedto K. Matsumoto (Asahi Chemical) on Mar. 28, 1989, teaches apositive-working photoresist stripper composition containing (A)gamma-butyrolactone, N-methylformamide, N,N-dimethylformamide,N,N-dimethylacetamide or N-methyl-2-pyrrolidinone; (B) an amino alcohol(e.g., N-butyl-ethanolamine and N-ethyldiethanolamine); and (C) water.

[0020] Japanese Published Patent Application No. 4-350660, which issuedto H. Goto et al. (Texas Instruments, Japan and Kanto Chemical, Inc.) onDec. 4, 1992, teaches a stripper for positive photoresists comprising(A) 1,3-dimethyl-2-imidazolidinone, (B) dimethylsulfoxide and (C) awater-soluble amine (e.g., monoethanolamine or 2-(2-aminoethoxy)ethanolwherein the amount of the water-soluble amine is 7-30% by weight.

[0021] Japanese Published Patent Application No. 7-271057, which waspublished on Oct. 20, 1997, and is assigned to Tokyo Ohka Kogyo, teachespositive photoresist compositions that contain N,N-diethylhydroxyamine.Preferred formulations also contained either alkanolamines (e.g.,monoethanolamine); water-miscible organic solvents (e.g.N-methyl-2-pyrrolidinone); water; additives (e.g., hydroxy aromaticcompounds or triazole compounds); or carboxylic group-containing organiccompounds, or certain combinations thereof. Salicyl alcohol is one ofthe preferred hydroxy aromatic compounds.

[0022] Japanese Published Patent Application No. 7-271057 does suggeststhe addition of carboxylic acid to an admixture of a water-misciblepolar solvent and an alkanolamine for the application to photoresiststripping composition or plasma-etch residue cleaning composition.However, that reference requires the presence of a hydroxylaminecompound, N,N-diethylhydroxylamine (DEHA), to achieve its desiredperformance.

[0023] Likewise European Patent Application No. 596515 does discloses anadmixture of a solvent, an alkanolamine and a non-nitrogen containingweak acid in its formulation. However, this composition does not containwater which is essential in the removal of some kinds of plasma etchresidues.

[0024] The stripping and cleaning composition of the present invention,on the other hand, is effective in removing a wide variety of bothorganic polymeric materials and plasma-etch residues. The inventor hasfound that some types of corrosion inhibitors can prevent metalcorrosion without any reduction in the stripping rate of photoresist, orany reduction in the effectiveness of removing plasma etch residues. Thepresent formulation provides a superior balance of various functionaland economic requirements, including excellent prevention of metalcontamination of substrate surfaces, and favorable material cost for thedesired corrosion inhibition effect.

SUMMARY OF THE INVENTION

[0025] The present invention is directed to a non-corrosive strippingand cleaning composition which is free of hydroxylamine and itsderivatives, this composition comprises:

[0026] (a) about 5% to 50% of a solvent selected from the groupconsisting of: N-methyl-2-pyrrolidinone, N-hydroxyethyl-2-pyrrolidinone,1,3-dimethyl-2-imidazolidinone, dimethylsulfoxide,N,N-dimethylacetamide, sulfolane, diacetone alcohol, ethylene glycol,propylene glycol and admixtures thereof;

[0027] (b) about 10% to 90% of an alkanolamine selected from the groupconsisting of: diethyleneglycolamine, monoethanolamine, diethanolamine,triethanolamine, 2-(2-aminoethylamino)ethanol, and admixtures thereof;

[0028] (c) about 0.1% to 10% of a carboxylic acid type corrosioninhibitor, the carboxylic acid type corrosion inhibitor being selectedfrom the group consisting of: formic acid, acetic acid, propionic acid,valeric acid, isovaleric acid, oxalic acid, malonic acid, succinic acid,glutaric acid, maleic acid, furmaric acid, phthalic acid,1,2,3-benzene-tricarboxylic acid, glycolic acid, lactic acid, citricacid, salicylic acid, tartaric acid, gluconic acid, and combinationsthereof; and

[0029] (d) about 1% to 40% of water.

[0030] All percentages above are by weight of the total weight of thestripping and cleaning composition.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] As defined herein, the term “non-corrosive” refers to suppressionof any chemical action that gradually wears away a substrate. The term“stripping and cleaning composition” refers to a composition that isable to both (1) remove or strip a photoresist (or other similar organicpolymeric material) film or layer from a substrate, and (2) remove orclean various types of plasma-etch residues (also sometimes calledplasma sidewall polymers) from a substrate.

[0032] As stated above, the non-corrosive stripping and cleaningcomposition of the present invention has four components, namely, one ormore selected polar solvents, one or more selected alkanolaminecompounds, one or more selected corrosion inhibitors; and water. Thesefour components must be present in certain percentages. Also, thepresent invention is preferably free of hydroxylamine compounds and itsderivatives such as N,N-diethylhydroxylamine.

[0033] Solvents used in the stripping and cleaning composition of theinvention include N-methyl-2-pyrrolidinone (NMP),N-hydroxyethyl-2-pyrrolidinone (HEP), 1,3-dimethyl-2-imidazolidinone(DMI), dimethylsulfoxide (DMSO), N,N-dimethylacetamide (DMAC),sulfolane, diacetone alcohol (DAAL), ethylene glycol (EG), propyleneglycol (PG) or combinations thereof. NMP and HEP are the preferredsolvents. These solvents are effective in stripping various types ofphotoresist.

[0034] Especially desirable is an admixture of HEP and NMP wherein themixing ratio of HEP to NMP, by weight % is from about 10:90% to 90:10%,as HEP is a safer and more viscous solvent, while NMP is a more powerfulstripping solvent with low viscosity. In general, the stripping power isincreased by lowering the viscosity of a stripper solution.

[0035] Alkanolamines are also included in the stripping and cleaningcomposition, as mentioned above. Preferred alkanolamines includediethyleneglycolamine (DEGA), monoethanolamine (MEA), diethanolamine(DEA), triethanolamine (TEA), 2-(2-aminoethylamino)ethanol andadmixtures thereof. MEA is especially preferred.

[0036] Corrosion inhibitors useful in the present invention arecarboxylic acid compounds. Preferred carboxylic acid compounds are:formic acid, acetic acid, propionic acid, valeric acid, isovaleric acid,oxalic acid, malonic acid, succinic acid, glutaric acid, maleic acid,furmaric acid, phthalic acid, 1,2,3-benzene-tricarboxylic acid, glycolicacid, lactic acid, citric acid, salicylic acid, tartaric acid, gluconicacid, and combinations thereof. More preferred carboxylic acid typecorrosion inhibitors are lactic acid, citric acid, succinic acid,salicyclic acid, phthalic acid, tartaric acid, and gluconic acid. Thisfamily of compounds has been found to effectively inhibit the corrosionwithout any reduction of the stripping power especially in combinationwith admixtures of all polar solvents, alkanolamines and water asdescribed above. These compounds provide a superior balance of variousfunctional and economic requirements, including excellent prevention ofmetal contamination of substrate surfaces, and favorable material costfor the desired corrosion inhibition effect.

[0037] The fourth critical ingredient is water. Water increases thecleaning power when the composition of the invention is used as acleaner of post-plasma etch residue.

[0038] Optional ingredients in the stripping and cleaning composition ofthe invention include water-soluble surface-active agents. Exemplarysurface-active agents include poly(ethylene oxide) condensates withfatty alcohols manufactured by Olin Corporation of Norwalk, Conn. underthe trade name of “POLY-TERGENT® CS-1”.

[0039] The preferred amounts of these ingredients are about 8-40% polarsolvent; about 20-80% amine compound; about 1 to 10% corrosioninhibitor; 5-35% water; and, if used, 0.01-2% surface-active compound;all based on the weight of the stripping and cleaning composition. Themore preferred amounts of these ingredients are about 10-35% polarsolvent; about 30-70% amine compound; about 3 to 7% corrosion inhibitor;about 10-30% water; and optionally about 0.05-1% surface-activecompound; all based on the weight of the total composition.

[0040] Various other ingredients known to those skill in the art mayoptionally be included in the stripping and cleaning composition, e.g.,dyes or colorants, wetting agents, antifoamers and so forth. Generally,the amount of each of these other optional ingredients would be about0.01-0.5% by weight, based on the total composition.

[0041] The stripping and cleaning composition of the invention isprepared by dissolving one or more selected corrosion inhibitors withone or more selected solvents and one or more selected alkanol compoundsat room temperature. As indicated above, optional ingredients may alsobe added.

[0042] One function of the described stripping and cleaning compositionis removal or stripping of organic polymeric material from a substrate.This aspect of the invention is carried out by contacting an organicpolymeric material such as a photoresist film with the describedstripping and cleaning composition. The above-described composition mayalso be used in removing post-plasma etch by-products after plasmaetching of a metallized wafer. These plasma-etch by-products are, forexample, oxides or halides of aluminum, titanium, copper or relatedmetals, such as, AlCl₃, AlF₃, Al₂O₃, SiF₄, SiO₂ and the like. Thisaspect of the invention is carried out by contacting the plasma-etchresidues with the described cleaner solution. The actual conditions,i.e., temperature, time, and the like, may vary over wide ranges and aregenerally dependent on the nature and thickness of the organic polymericmaterial or plasma-etch residue to be removed, as well as other factorsfamiliar to those skilled in the art. In general, however, temperaturesranging from about 45° C. to 90° C. for a period of about 5 minutes to40 minutes are typical.

[0043] A variety of means can be employed in contacting the organicpolymeric material and/or plasma-etch residues with the stripping andcleaning composition in the practice of the invention. For example, thesubstrate containing the organic polymeric material and/or plasma-etchresidue can be immersed in a stripping and cleaning bath or thestripping and cleaning composition can be sprayed over the surface ofthe organic polymeric material, as well as plasma-etch residues, as willbe apparent to those skilled in the art.

[0044] The stripping and cleaning composition of the invention iseffective in removing a wide variety of organic polymeric materials andplasma-etch residues from substrates. Exemplary organic polymericmaterials include positive- and negative-working g-line, i-line and deepUV resists, electron beam resists, X-ray resists, ion beam resists, aswell as organic dielectric materials such as polyimide resins, and soforth. Specific examples of organic polymeric materials which can beremoved in the practice of the invention include positive resistscontaining phenol-formaldehyde resins or poly(p-vinylphenol), negativeresists containing cyclized polyisoprene, or poly(p-vinylphenol); andpolymethylmethacrylate-containing resists. In particular, the strippingand cleaning composition has been found to be highly effective inremoving positive resists containing a novolak resin and adiazonathoquinone type sensitizer, e.g., ortho naphthoquinone diazidesulfonic acid ester. Resists of this type include HPR 204 SeriesPOSITIVE RESIST, HPR 504 Series POSITIVE RESIST, OiR32 Series POSITIVERESIST, and HPR 6500 Series POSITIVE RESIST, sold by OlinMicroelectronic Materials, of Norwalk, Conn. The organic polymericmaterial residues can be removed from any of the conventional substratesknown to those skilled in the art, such as silicon, silicon dioxide,silicon nitride, polysilicon, aluminum, aluminum alloys, copper, copperalloys, polyimides, and so forth.

[0045] The present invention is further described in detail by means ofthe following examples. All parts and percentages are by weight and alltemperatures are degrees Celsius unless explicitly stated otherwise.

EXAMPLE 1

[0046] A stripping/cleaning solution was prepared by mixing 30.0 g ofN-methyl-2-pyrrolidinone (NM), 55.0 g of monoethanolamine (MEA), 5.68 gof 88 wt. % of lactic acid (LA) solution in water, and 9.32 g ofdeionized water with stirring to produce a clear solution. The ratio byweight of the components in the resulting solution wasNMP/MEA/H₂O/LA=30.0/55.0/10.0/5.0. The pH of the solution was 11.8.

[0047] Silicon wafers which have a multi-layer of Al—Cu—Si/SiO₂/Si wereprepared by plasma deposition method and further top-coated with apositive photoresist (PR) at a film thickness of 1.0 micron by spincoating method. Micropatterning was applied to the PR layerphotolithographically, followed by pattern transfer onto the metal layerby plasma etching with the prepatternized PR mask. Thus obtained waferscontained both residues of PR and plasma etching by-products which werea mixture of silicon and aluminum oxides and halides. The composition ofthe resulting plasma-etch residues (PER) were characterized by x-rayspectroscopy.

[0048] The wafers obtained were cut into 1 cm×1 cm pieces and placed ina 200 ml beaker which contained 100 ml of the above-mentionedstripping/cleaning solution in a temperature-controlled bath at 70° C.The pieces of wafer were immersed in the solution with gentle agitationfor 30 minutes. The wafer pieces were transferred to another beaker thatcontained deionized water at room temperature and gently stirred for 5minutes. The wafer pieces were then removed from the water and dried byblowing nitrogen gas onto the surface of the wafer pieces.

[0049] The wafer pieces were inspected under a scanning electronmicroscope (SEM) after gold sputtering. Top-down and cross-section viewsof the wafer SEM pictures were obtained to visualize the residue of PRand PER on the wafers. In addition, the exposed metal layer surface wasinspected under SEM to evaluate any corrosion of the metal surface.

[0050] The SEM inspection results indicated that the present formulationof NMP/MEA/H₂O/LA=30/55/10/5 removed both residues of PR and PER withoutmetal corrosion even if the post-strip intermediate rinse with anorganic solvent such as isopropyl alcohol (IPA) was not applied.

EXAMPLES 2-3

[0051] Examples 2-3 illustrate additional compositions tested withadmixtures of the same solvent, alkanolamine, water and lactic acid atdifferent concentrations. Detailed formulations are summarized in Table1 with the SEM inspection of each result.

CONTROL 1

[0052] In addition to Examples 1-3, a control formulation that containedno corrosion inhibitor was prepared as follows: NMP/MEA/H₂O=35/55/10.The strip test condition was the same as described in Example 1.

[0053] The SEM inspection result showed that both residues of PR and PERwere completely removed as shown in Example 1. However, the metal layerwas severely corroded in comparison to the formulations of Examples 1-3.

CONTROL 2

[0054] In addition to control 1, another control formulation that didnot contain water was prepared as follows: NMP/MEA/LA=35/60/5. The striptest condition was the same as described in Example 1.

[0055] The SEM inspection showed that while PR residue was completelyremoved, the formulation without water did not remove the plasma-etchresidues. Also, as shown in Table 1, no metal corrosion was observedwith this formulation.

[0056] Table 1 below shows the results of the different formulations andtheir affect on stripping of the Photoresist (PR), Plasma Etch Residuescleaning (PER) and Corrosion inhibition (CIN). TABLE 1 Formulation (Wt.%) Performance Example NMP MEA H₂O LA PR PER CIN 1 30 55 10 5 +++ ++++++ 2 34 55 10 1 +++ +++ + 3 32 55 10 3 +++ +++ ++ Control 1 35 55 10 0+++ +++ − Control 2 35 60  0 5 +++ − +++

[0057] The following conclusions may be drawn from the result shown inTable 1:

[0058] (1) The addition of lactic acid to the mixture of solvent,alkanolamine and water is essential to prevent the metal corrosionwithout any drawback of the performance of the photoresist stripping andplasma-etch residue cleaning;

[0059] (2) There is a concentration dependency of lactic acid on thecorrosion inhibition. In other words, there should be an optimumconcentration of lactic acid to make the best balance of the corrosioninhibition vs. the residue removal; and

[0060] (3) The absence of water with the mixture of solvent,alkanolamine and lactic acid results in the incomplete removal of theplasma-etch residues.

[0061] While the invention has been described above with reference tospecific embodiments thereof, it is apparent that many changes,modifications, and variations can be made without departing from theinventive concept disclosed herein. Accordingly, it is intended that thepresent invention embrace all such changes, modifications, andvariations that fall within the spirit and broad scope of the appendedclaims.

What is claimed is:
 1. A non-corrosive stripping and cleaningcomposition, which is free of hydroxylamine and its derivatives,comprising: (a) about 5% to 50% by weight of a solvent selected from thegroup consisting of: N-methyl-2-pyrrolidinone,N-hydroxyethyl-2-pyrrolidinone, 1,3-dimethyl-2-imidazolidinone,dimethylsulfoxide, N,N-dimethylacetamide, sulfolane, diacetone alcohol,ethylene glycol, propylene glycol and admixtures thereof; (b) about 10%to 90% by weight of an alkanolamine selected from the group consistingof: diethyleneglycolamine, monoethanolamine, diethanolamine,triethanolamine, 2-(2-aminoethylamino)ethanol, and admixtures thereof;(c) about 0.1% to 10% by weight of a carboxylic acid type corrosioninhibitor; and (d) about 1% to 40% by weight of water.
 2. Thenon-corrosive stripping and cleaning composition of claim 1 , whereinsaid carboxylic acid corrosion inhibitor is selected from the groupconsisting of: formic acid, acetic acid, propionic acid, valeric acid,isovaleric acid, oxalic acid, malonic acid, succinic acid, glutaricacid, maleic acid, furmaric acid, phthalic acid,1,2,3-benzene-tricarboxylic acid, glycolic acid, lactic acid, citricacid, salicylic acid, tartaric acid, gluconic acid, and combinationsthereof.
 3. The non-corrosive stripping and cleaning composition ofclaim 1 , wherein said solvent is present in the range between about8-40%, said alkanolamine is present in the range between about 20-80%,said corrosion inhibitor is present in the range between about 1 to 10%,and said water is present in the range between about 5-35%.
 4. Thenon-corrosive stripping and cleaning composition of claim 1 , whereinsaid solvent is present in the range between about 10-35%, saidalkanolamine is present in the range between about 30-70%, saidcorrosion inhibitor is present in the range between about 3 to 7%, andsaid water is present in the range between about 10-30%.
 5. Thenon-corrosive stripping and cleaning composition of claim 1 , furthercomprising about 0.01% to 2% by weight of a surface-active compound. 6.A non-corrosive stripping and cleaning composition, which is free ofhydroxylamine and its derivatives, comprising: (a) about 8-40% by weightN-methyl-2-pyrrolidinone; (b) about 20-80% by weight monoethanolamine;(c) about 3 to 7% by weight lactic acid; and (d) about 5-35% water.